Apparatus for induction hardening of anti-wear mechanical members

ABSTRACT

A flat, anti-wear mechanical member, which the mating member moves in sliding contact with, characterized by the fact that it is induction hardened at the surface layer thereof in such manner as to form many separate hardened layers which are distributed in the surface layer radially and concentrically with respect to the center of the surface of the member; a process for the induction hardening of a flat member, characterized by supporting an induction heating coil above a radius vector of the surface layer to be hardened of the flat member so that an alternate magnetic flux density is kept uniform throughout the surface layer by flowing a high frequency electric current intermittently through the heating coil while revolving the member, thereby to form many separate hardened layers which are distributed as mentioned above; and an apparatus for the practice of the process.

Oct. 31, 1972 United States Patent Gomada et al.

XXX 777 .1 000 ll] a m re SMGA I both of Hiroshima Japan Primary Examiner-R. F. Staubly [73] Assigneez. Toyo Kogyo Co., Ltd., Hiroshima- Assistant Examiner-B. A.- Reynolds k n,' P AttorneyRalph E. Bucknam, Jesse D. Reingold,

Robert R. Strack and Henry A. Marzullo, Jr.

[22] Filed: Dec. 9, 1970 [211 Appl.No.: 96,659

, ABSTRACT Related [1.8. Application Data A flat, anti-wear mechanical member, which the mat- 62 f S N 754, ing member moves in sliding contact with, charac- 1 mslon 0 er 0 340 terized by the fact that it is induction hardened at the Aug. 21, .1968,

surface layer thereof in such manner as to form many Pat. No. 3,647,577.

[30] Foreign Application Priority Data' separate hardened layers which are distributed in the Aug. 30, 1967 Sept. 4, 1967 surface layer radially and concentrically with respect to the center of the surface of the member; a process Japan ......................42/5560l J for the induction hardening of a flat member, charact ed b su rt'n an induction heatin coil abo ,219Il0.69, em y ppo g g W [52] US. Cl.

219/1057 219/1043 a radius vector of the surface layer to be hardened of the flat member so that an alternate magnetic flux [51] Int.

density is kept uniform throughout the surface layer by flowing a high frequency electric current intermit- [58] Field of sea -cu.jii wioieil ioiiil 10.75, 10.41,

219/1043 1057 tently through the heating coil while revolving the [56] References Cited member, thereby to form many separate hardened UNITED STATES PATENTS 1/1940 Endsley.........

layers which are distributed as mentioned above; and an apparatus for the practice of the process.

.....2l9/ 10.77 X 7 Claims, 11 Drawing Figures h m II I PATENTEDncI 3 1 1912 sum 1 or 3 IHHlunu PATENTEDUEI31 I912 3.701.874

SHEET 2 OF 3 HIGH FREQUENCY POWER SOURCE OSCILLATION ORDER I f A 83080 .LHVLS 83080 HSAO-BSNVHQ dWV'l PATENTEDUBTQI I972 sum 3 or 3 30 OPERATION TIME (HrQ) Flair FIG.9

FlG.8

FIGQII FIGJO trically with respect'to the center of the surface of the member, to a flat member quench hardened by the process and to an apparatus adapted for the practice of the process. i

The invention has for its object the efficient manufacture of hardened members having always sufficientv strength and wear resistance for the intended applications by, effecting .the hardening in such way as to reduce the quenching strain or warpingand minimize theallowance forfiriishing as by grinding. I

As is well known, in the induction-hardening of a flat member orworkon the surface alone, the customary practice of hardening the entire surface involves such a high degree of quenching strain (i.e., warpage) that the dimensional accuracy of flatness is materially adversely affected. Moreover, subsequent grinding or other finish machining of the hardenedsurface will locally remove much of the hardened layer, thus rendering it difficult to obtain a final hardened layer of uniform hardening depth or penetration and hence to obtain a finished articl e with a uniform wear resistance. In view of these are required toicombine good mechanical properties with wear resistance, the hardening penetration must be limited to a minimum in order to avoid sacrificing their mechanical properties. Thus, quenching hardening to a greater depth of a member presents problems, and the surface hardening of the member as desired has been considered to be very difficult to effect.

The present invention is directed to overcome the foregoing difficulties of the conventional processes, and is based on a finding that when the surface layer of a flat member is partially hardened so that many separate hardened layers are formed side by side radially and concentrically in the surface layer as hereinafter fully described, the resulting warpage of the I 2 throughout its surface layer in accordance with the present invention, a member will have a quenching strain remarkably less than that produced by the conventional processes. (Separate hardened layers distributed radially and concentrically in the surface layer of a member mean herein the ones distributed as shown in FIG. l to be hereinafter described.) The two areidentical in that most of the strain caused by the hardening is. absorbed by the rest of the surface which is not hardened. The difference thenseems attributable to the act that in the former the directional character of hardening causes a buildup of residual strain left unabsorbed due to the increases in the hardness penetration, number of hardened stripes and the width of individual stripes, while in the latter the lack of directionality results in only a negligible buildup of strain.

FIG. 1 is a plan view of an induction hardened member the surface layer of which is hardened in such manner as to form many separate hardened layers which are distributed inthe surface layer radially and concentrically? with respect to the center of the surface of the member; I I I FIG. 2 is a fragmentary verticaly sectional view taken along the line A-'A of FIG. I, I I

FIG; 3 is a side view of a fragment of the member shown in FIG. 1;

FIG. 4.is a vertical sectional vew of the essential member of a quench hardening apparatus'sho'wing how a coil for induction heating is set in position;

FIG. 5 is an enlarged sectional view taken along the line B-B of FIG. 4;

FIG. 6 is a block diagram illustrating a form of control mechanism for thehar'clening apparatus;

FIGS. 7 and 8 are plan views showing members of other contours to be hardened;

FIG. 9 is a graph showing a comparison of frictional loss between the mating members which move in-sliding contact respectively with the hardened member of this invention and with the conventional hardened member;

FIG. 10 is a vertical sectional view of a rotary piston engine to which hardened members of this invention are applied; and

FIG; 11 is a side view of the rotary piston engine from which one of the side housings is removed.

In order to provide a member with a wear resistance as uniform throughout its surface as possible by partially hardening the surface in accordance with the present invention, certain conditions including the following must be'satisfied. As illustrated in FIGS. 1 to 3, (l) hardening penetration or depth at given points of the hardened layers 2 of a hardened member 1 must be substantially the same, i.e., d, d d (1,, (2) on a circle of a given radius r from an origin which is the center 0 of the hardened member 1, the ratio of the sum of individual arcs representing the hardened layers to the circumference must be kept substantially constant, i.e.,

(where 1 represents the length of arc; n, number of separate hardened layers; r, the radius, and c, the constant), and (3) as many'separate hardened layers as possible are formed. 'To meet these requirements, the

present invention relies upon a hardening procedure now to be described.

, motor via reduction gear. An induction heating coil 8 which is provided with a ferrite core 6 and a number of ports for cooling water 7, is connected to a high frequency oscillator 9 and is held above the member 1 so that it covers the radius vector R of the latter. This induction heating coil 8 is supported adjustably inposition vertically by the usual means in order to meet the variation in height H of the member 1. The coil is also arranged so that it can be withdrawn integrally with the support means from above the table 4 when the member 1 is to be placed in or out of the working position. An alternative arrangement may be provided whereby the table 4 can recede in place of the induction coil 8. Whilethe ports 7 for cooling water are so formed at a suitable angle in the heating coil 8 as shown in FIG. that they will not permit the cooling water to flow over unhardened area ofthe member, it is desirable to combine this with a slightly slant installation of the apparatus as a-whole, or with blowing of air from the opposite side in order to prevent the water from flowing over the unhardened area.

In hardening a member or workpiece having a hole or holes, the well-known technique of avoiding unnecessary hardening operation over the void by inserting a copper plug in each hole may of course be adopted. In the case of a member 1 having a round hole 1 in the center as shown in FIG. 7, or a member I having a round portion 1 inthe center that is not to be hardened as shown in FIG. 8, it is possible to harden the desired surface only by displacing the induction heating coil 8 beforehand by a distance r or r toward the periphery along the radius vector from the rotation center 0 of the member. I

In order to ensure uniformity of hardening depth or penetration at given points of the individual hardened layers, the alternate magnetic flux density per unit area of the surface being hardened must be kept constant. Thus, if a desired depth of hardening d is given with a constant power supply, the coil 8 for induction heating is set in the following way. In consideration of the heat ing efficiency, prevention of spark, and other factors, the gap t between the coil 8 and the member 1 reaches an optimum minimum (t along theperiphery of the maximum radius vector (R,,,,,,), and the revolution velocity of the table is so adjusted that desired hardening depth d will be obtained and the velocity so adjusted is regarded as the basic velocity. It is now only necessary to tilt the induction heating coil 8 at a desired angle on the basis of the optimum minimum gap so that the hardening penetration at given points between the center of hardened layers and the outer periphery may be kept substantially the same at this basic velocity. In this embodiment of the invention, uniformity of hardening penetration is further ensured by suitably adjusting the cross sectional area of the ferrite core 6 according to the values of the alternate magnetic flux and gap t, as shown in FIGS. 4 and 5. When the coil 8 for induction heating equipped with the ferrite core 6 is provided over the radius vector of a circular member as stated above and when a high frequency current is ap plied to the coil at regular intervals for a predetermined period of time while turning the table at the basic velocity,- then the circular member can be hardened as desired on thesurface. v

In the case of a noncircular member, however, the alternate magnetic flux density per unit area of the member surface varies with the change of the area covered by the coil per unit time or, stated differently, in inverse proportion to the square of the length of radius vector of the member (in case of FIGS. 7 and 8,

R, r,? and R r ,respectively) when the table is turned uniformly at the basic velocity. Therefore, in order that the. hardening penetration be made substantially constant at given points of the hardened layers on the noncircular member, it is necessary to control the turning of the table in such manner that the area velocity of the member surface to be hardened (the surface area to be covered by R in FIG. 1 or by R r and R r, in FIGS. 7 and 8, respectively, as the table turns) be kept constant depending upon the length of radius vector of the member. I

According to the present invention, the above-mentioned arrangement is controlled by a control mechanism for governing the turning speed of the table in accordance with a program that divides the member surface beforehand intoia number of equi-angular sectors with the center of revolution as the origin for the reason above stated, preferably establishing arelationship of n am where a is a positive integer and n the number'of hardened layers, and renders the average area velocity of the member surface in the respective regions thus divided constant as a rule, while adjusting the hardening penetration locally where desired, and also by a two-system control mechanism for controlling the number of hardened layers and the hardening intervals by similarly dividing the member surface into equiangular sectors or dividing the period of time required for each revolution of the member into periods of equal length and then heating the member surface for a predetermined period of time within the confines of such divisions.

The control mechanisms will now be explained specifically by reference to FIG. 6. As shown, the revolution of the shaft 19 of a motor 18 equipped with a reduction gear is reduced through gears 20, 21 and transmitted to a worm shaft 22 The speed is further decreased by a worm 23 and a worm gear 24, so that the table 4 mounted on the spindle 3 can be turned at a very low speed. In the table turning mechanism of the construction above described, a cam plate 26 formed with a desired number of rectangular lobes 25 is fitted to the worm shaft 22, and limit switch means such as an approach switch 27 or microswitch is provided in close '5 latter by a certain angle in the turning direction thereof, a limit switch 28 is set in the proximity of a position ahead by the above-said angle of a rectangular protuberance'30 of a cam plate 29 which is fitted to the spindle 3 of the table 4, so that the initiation and stopping positions for hardening can be detected. A speed control panel 3 1, which is a variety of graphic panel, comprises a dial 32 for basic speed setting and a plurality of sub-dials 33 for speed ratio setting, whereby the variations of turning speed of the table'4 in different regions are pre-set or beforehand set in terms of slectrical amounts. Thepanel is also provided with a line 34 that represents the contour of member surface to be hardened, sectoral pilot lamps 35, arrow lamps 36 indicating the turning directions, quadrant pilot lamp 37, etc. which all serve to indicate the progress of hardening operation. Setting of this panel will now be described specifically in connection with the member l shown in FIG. 1. ln turning the table 4 successively in the direction indicated by asolidarrow along the line 34, the dial 32 is set to a standard table turning speed which is governed by the type of the coil for induction heating and the manner in which the coil is held in working position. Next, the speedratio setting sub-dial 33a for the first sector is set to a speed ratio of l to serve as a standard dial, The rest of subdials 33 arethen set to different values of speed ratios required to render the area velocity of .the member surface constant.

Where it is desired to vary the hardening penetration in certain sectors of the member or where the turning ing coil or work coil 8 to. a predetermined point above speed of the table is to beincreased for certain sectors speed settings, the sectoral pilot lamps are lighted in succession along the line 34, first in the direction indicated by a solid arrow and thenbackward inthe direction indicated by a dotted arrow, thus serving together with the directional pilot lamps36 and quadrant pilot lamp 37 to indicate the progress of the hardening operation.

On the speed control panel 31, the number of subdials 33 provided for speed ratio setting varies depending on the contour of the member to be hardened regardless of whether the number of separate hardened layers or portions is same or not. For example, it is one half of and equal to the'number of sectors m of the members shown in FIGS. 7 and 8, respectively. The panel may be re-designed for any desired rearrangement of the pilot lamps, and the lamps may be omitted where unnecessary.

A control circuit 38 is so designed that, in response to a command from an operation panel 39 and upon receipt of signals from the limit switch 28 and approach switch 27, it gives necessary orders to a firing control circuit 40, a high frequency oscillating circuit 41 and a pre-set input change-over circuit 42 thereby to actuate the respective electric circuits.

The operation of the system will now be described. If a member 1 to be hardened is placed securely on the 'table 4 and the starting push button on the operation panel 39 is pressed, the control circuit 38 will instruct a solenoid valve (not shown) to move the induction heatthe member surface and, at the same time, give a start order to the firing control circuit 40. Since the pre -set input change-over circuit 42 is connected to the dial 32 and sub-dial 33a on the speed control panel 31 and an amount of electricity corresponding to the basic speed setting is given as input to the firing control circuit 40, the firing control circuit 40 upon receipt of the start order will work correspondingly to the input to actuate a rectifier circuit 43'and thereby drive the motor 18 at a desired speed. Then, the coil 8 will move to -a tion with the speed ratio setting sub-dials 33 on the speed control panel 31 to change the turning speed of the table4 accordingly by way of the firing control circuit 31 andrectifier circuit 43.

Meanwhile, from this point of time, the control circuit 38 upon receipt of veach signal from the approach switch 27 will give an oscillating signal to the high frequency oscillating circuit 41, so that a high frequency current is intermittently flown through the coil 8 as it is supplied to the coil from the high frequency oscillating circuit 41 for intermittent periods of time pre-set by the timer 44 on the operation panel 39, whereby the member'is hardened in radial streaks of parallel thin zones forming equidistantly broken concentric circles. in the case when the ratio of the total area of separate hardened layers to that of the remaining unhardened layers is desired to be kept constant, the .timerequired for each turn of the table'4 is divided into equal time portions, eachbeing 1/n of the total time, and the timer 45 on the operation panel 39 is set to these time portions and the change-over switch on the operation panel 39 is switched over to the equal time division, all

before the starting of the-operation. Thenfthe control circuit 38 will'generate oscillating signals at the intervals of time pre-set on the timer 45, and in this case again the member. will be partially hardened on the surface in the specific hardening pattern according to this invention. According to this equal time division system, narrower hardened layers are formed in closer order in the surface portion in which the radius vector is long than in the portion in which the vector is less long. In this case the signals from the approach switch 27 are used solely for the detection of the points of time for sending input change-over signals and initial oscillating I signals.

commands the firing control circuit 40 to stop. After the table 4 has been stopped accordingly, the control circuit 38 further gives a reversing command to the table 4, which is then reversed at the basic speed to the starting position and is stopped there in preparation for the next hardening cycle. I

the same speed as that of the turntable 4. If, in this case,

the center angles of the arcs of lobes are kept constant in such way that the arcuate lengths of the lobes serve, in place of the timer 44, to provide the time intervals for. the supply of electricity, the area ratio of separate hardened layers and the remaining unhardened ones at any surface portion of the member can also be rendered substantially constant in the equi-angular division system. Also, instead of the setting section of the type using the speed ratio setting dials, a cam plate of the same contour as the member surface may be provided so that the length .of rotatory radius vector can be detected as by a potentiometer to effect continuous variation of the turning speed of the table 4. Generally, however, the system using dials permits the electric circuits to be simplified in construction and adjusted with ease. A further advantage of this system is that it is applicable to members of the contours as shown in FIGS. 7 and 8 as well without the necessity of adding any special circuit to its original circuit.

In the block diagram the electric circuits illustrated may of course be those generally in use and the individual electric circuits may be modified or redesigned in a number of ways. Therefore, explanation in detail of these circuits and their specific connection diagrams are omitted here.

While the process of the present invention has so far been described in conjunction with a procedure whereby a member is hardened in the surface layer to form separate, linear hardened layers which are distributed in the surface layer radially and concentrically with respect to the center of the'member, as shown in FIG. 1, it is alternatively possible to provide separate hardened layers in other desirable forms, e.g., a spiral or wavy formation, distributed in the same way as mentioned above. To attain this, it is only necessary to use an induction heating -coil of a correspondingly modified surface contour or form.

This invention will be better understood by the following examples.

EXAMPLE I An oval-shaped, thin-walled member madeof special cast iron, measuring 250 mm in major axis, 190 mm in -minor axis and 40 mm in height, and having a center hole with an inside diameter of 75 mm, and which was mm thick at the portion to be hardened, was placed securely on a table. A coil for induction heating equipped with a ferrite core and which measured 110 mm in length and had a cross section of 8 mm by 8 mm was held in position above the radius vector of the member. While the member was being turned at a velocity of 0.25 to 0.5 rpm, it was hardened so that 72 separate hardened layers were formed in the surface layer in the radial and concentric pattern of distribution thereof as previously mentioned by flowing intermittently a high frequency current of 57 KW through the coil from a vacuum-tube high frequency oscillator with a frequency of 200 KC and output of 75 KW, by means of the isochronous division system with a time ratio 3:2 of hardening interval to heating. The total warpages of the test pieces hardened in this way were invariably within the range of 0.1 l to 0.19 mm, or approximately one-third of those of test pieces conventionally hardened over the entire surface which range from 0.35 to 0.60 mm. The hardened faces were ground and then tested on an abrasion tester with a predetermined sliding piece held in pressure contact therewith under a certain load while the piece was being revolved at a high velocity on the tester. The test demonstrated that the member hardened in accordance with the present invention is similar or rather superior in wear resistance. to the conventional products.

EXAMPLE 2 Each of side housings of special cast iron for a rotary piston engine, measuring 300 mm in major axis, 260 mm in minor axis, 40 mm in height and .5 mm in thickness at the inner wall thereof the surface of which was to be hardened, and having a center hole of mm in inner diameter, was quench hardened according to this invention so that 72 separate, linear hardened layers of each approximately 1 mm in depth were formed in the same pattern of distribution thereof as in FIG. 1, the total area of these hardened layers being nearly 60 percent of that of the inner wall wherein they were formed. I v

The amount of warping of each of the side housings so hardened was within the range of 0.12 to 0.21 mm,

or approximately one-third of that of the side housing The test showed that the housing hardened according to this invention is equal or somewhat superior in wear resistance to the conventional ones. As further indicated in FIG. 9 which shows a frictional loss curves a and b for said housing partially hardened on the surface according to this invention andthe conventional one entirely hardened throughout the surface, respectively, it has been found that the frictional loss for the former is approximately half that for the latter and the former can decrease the mating member, which moves in sliding contact therewith, in frictional loss.

As shown in FIGS. 10 and 11, in general, a rotary piston engine comprises a casing formed of a center housing 11 and side housings 12; a rotor 13 which is housed in the casing and makes an eccentric rotation while keeping air-tight the spaces between the casing and the rotor with aid of apex seals 14, side seals 15 and corner seals 16, with which the rotor body is fitted, to repeata four-stroke cycle operation consisting of intake, compression, explosion (power) and exhaust.

thereby transmitting the power so obtained to a rotating shaft 17; and the rotating shaft 17. In a rotary piston engine, when the side housings. 12 hardened on the inner side according to this invention are applied, the 7 side seals 15 will uniformly be worn because of their sliding movement made astride the separate hardened layers 2 of the side housings l2 and will have a re hardened layers is large.

' Thus, when other members than the side housings for a rotary piston enginev are hardened according to this invention so that the mating member may slide on the hardened member astride the separate hardened layers formed in'the surface portion of the latter, the mating member will have a longer life-time when in use. For example, side housings for a vane-type rotary compressor may be hardened according to this invention so that individual hardened layers are formed in spiral form whereby the vanes of the compressor are decreased in frictional loss and have a longer life-time when in use.

As has been described above, the present invention is directed to hardening of a member by holding a coil for induction heating over the radius vector of the surface to be hardened'of a member being turned on a turntable, in such mannerthat the alternate magnetic flux density is rendered generally uniform on the surface, and flowing a high. frequency. current intermittently through the coil while the member is being continuously revolved, thereby forming separate hardened layers in the surface portion in such radial and concentric pattern of distribution thereof as shown in F IG. 1. Therefore, the process and apparatus of this invention are applicable to the surface hardening of flat articles with a number of advantages. Not only is uniform hardening penetration attained but the quenching strain is minimized and the grinding after quenching can be accomplished within an extremely short period of time by the practice of this invention. Furthermore,

'the articles thus hardened possess very good wear resistance. These desirable products can be obtained with a high degree of efficiency in accordance with the present invention.

Further advantages of more uniform hardening penetration andi more improved quality of hardened members will be obtained by carrying out a modified process wherein, as a rule, green members are hardened while being continuously revolved under the gradual or continuous control of speed so as to render the area velocity of the member surface constant. Even greater qualitative improvements of hardened workpieces will be made possible by carrying out the hardening operation with a high frequency current passed through the coil intermittently at isochronously divided intervals, because the area ratio of the hardened layers and the unhardened ones at any surface portion of the member can thereby be rendered substantially constant.

What is claimed is:

1. An apparatus for the production of a mechanical member with a flat anti-wear surface containing separate hardened layers distributed on the surface radially and concentrically with respect to a predetermined point on said surface, comprising:

A. A turntable which is revolved by a motor and on which a mechanical member with a flat surface to be quench hardened to form said flatanti-wear surface can be securely placed, I

B. An induction heating coil supported above a radius vector of the surface of the member revolved together with said turntable and adjusted so that the density of alternate magnetic, flux provided by said coil is kept substantially constant at said surface of the member,

C. A source for supplying a high frequency current to said coil,

D. A detecting means for detecting the initiating and stopping position for quench hardening and also for detecting each of equi-angular sectors which is obtained by equi-angularly dividing the angle of the revolution of said turntable into a suitable number determined depending mainly upon the shape of the surface of the member,

E. A control means responsive to said detecting means for controlling the turning speed of said turntable so that the average area velocity of the surface of the member in each equi-angular sectors is kept substantially constant and also for controlling the high frequency current supplied to said coil so that the magnetic flux is provided by said coil intermittently and also is provided for a predetermined period of time when it occurs.

2. An apparatus according to claim 1, wherein said control means controls the high frequency current supplied to said coil so that the magnetic flux is provided by said coil when said turntable revolves every predetermined angle. g

3. An apparatus according to claim 1, wherein said control means controls the high frequency current supplied to said coil so that the magnetic flux is provided by said coil at a constant interval of time.

4. An apparatus for the production of a mechanical member with a fiat anti-wear surface containing separate hardened layers distributed on the surface radially and concentrically with'respect to a predetermined point on said surface, comprising:

A. A turntable which is revolved by a motor and on which a mechanical member with a flat surface to be quench hardened to form said flat anti-wear surface can be securely placed,

B. An. induction heating coil supported above a radius vector of the surface of the member revolved together with said turntable and slanted with respect to the surface of the member so that: the density of alternate magnetic flux provided by ing each of equi-angular sectors which is obtained by equi-angularly dividing the angle of the revolution of said turntable into a suitable number detersu'rface of the member, ELA control means responsive to said detecting means for controlling the turning speed of said turntable so that the average area velocity of the surface of the member in each equi-angular sectors is kept substantially constant and also for controlling the high frequency current supplied to said coil so that the magnetic flux is provided by said mined depending mainly upon the shape of the v coil intermittently and also is provided for a predetermined period of time when it occurs.

5. An apparatus according to claim 4, wherein said control means including a setting unit for electrically setting the turning speed of said turntable in each equiangular sectors and the period of time while the high frequency current is supplied, a rectifier circuit responsive to the commands and signals from said setting unit and said detecting means for controlling the turning speed of said turntable, and a high frequency oscilation circuit responsive to the commands and signals from said setting unit and said detecting means for supplying the high frequency current to said coil intermittently and for supplying the high frequency current to said coil for a predetermined period of time when it occurs.

6 An induction hardening apparatus which comprises a turntable for supporting and rotating a workpiece to be induction hardened, and induction heating coil positioned in spaced apart relation to said turntable and to overlie the workpiece supported thereby, means for supplying a high frequency current to said coil to energize same and thereby induction heat portions of the workpiece passing by the coil during rotation of the workpiece by the turntable, means for delivering a quenching fluid to the workpiece to quench and thereby harden portions thereof that have been induction heated, and means responsive to the movement of said turntable and operable to regulate the energization of said coil by said high frequency current supply means in accordance with the angular position of the turntable to induction heat the workpiece intermittantly over angularly spaced regions.

7. An induction hardening apparatus according to claim 6 wherein said heating coil is hollow to accommodate the flow of quenching fluid, and has apertures positioned to discharge quenching fluid against the workpiece. 

1. An apparatus for the production of a mechanical member with a flat anti-wear surface containing separate hardened layers distributed on the surface radially and concentrically with respect to a predetermined pOint on said surface, comprising: A. A turntable which is revolved by a motor and on which a mechanical member with a flat surface to be quench hardened to form said flat anti-wear surface can be securely placed, B. An induction heating coil supported above a radius vector of the surface of the member revolved together with said turntable and adjusted so that the density of alternate magnetic flux provided by said coil is kept substantially constant at said surface of the member, C. A source for supplying a high frequency current to said coil, D. A detecting means for detecting the initiating and stopping position for quench hardening and also for detecting each of equi-angular sectors which is obtained by equi-angularly dividing the angle of the revolution of said turntable into a suitable number determined depending mainly upon the shape of the surface of the member, E. A control means responsive to said detecting means for controlling the turning speed of said turntable so that the average area velocity of the surface of the member in each equi-angular sectors is kept substantially constant and also for controlling the high frequency current supplied to said coil so that the magnetic flux is provided by said coil intermittently and also is provided for a predetermined period of time when it occurs.
 2. An apparatus according to claim 1, wherein said control means controls the high frequency current supplied to said coil so that the magnetic flux is provided by said coil when said turntable revolves every predetermined angle.
 3. An apparatus according to claim 1, wherein said control means controls the high frequency current supplied to said coil so that the magnetic flux is provided by said coil at a constant interval of time.
 4. An apparatus for the production of a mechanical member with a flat anti-wear surface containing separate hardened layers distributed on the surface radially and concentrically with respect to a predetermined point on said surface, comprising: A. A turntable which is revolved by a motor and on which a mechanical member with a flat surface to be quench hardened to form said flat anti-wear surface can be securely placed, B. An induction heating coil supported above a radius vector of the surface of the member revolved together with said turntable and slanted with respect to the surface of the member so that the density of alternate magnetic flux provided by said coil is kept substantially constant at said surface of the member, C. A source for supplying a high frequency current to said coil, D. A detecting means including a limit switch means and a cam plate revolved synchroneously with said turntable and detecting the initiating and stopping position for quench hardening and also for detecting each of equi-angular sectors which is obtained by equi-angularly dividing the angle of the revolution of said turntable into a suitable number determined depending mainly upon the shape of the surface of the member, E. A control means responsive to said detecting means for controlling the turning speed of said turntable so that the average area velocity of the surface of the member in each equi-angular sectors is kept substantially constant and also for controlling the high frequency current supplied to said coil so that the magnetic flux is provided by said coil intermittently and also is provided for a predetermined period of time when it occurs.
 5. An apparatus according to claim 4, wherein said control means including a setting unit for electrically setting the turning speed of said turntable in each equi-angular sectors and the period of time while the high frequency current is supplied, a rectifier circuit responsive to the commands and signals from said setting unit and said detecting means for controlling the turning speed of said turntable, and a high frequency oscilation circuit responsive to the commands and signals from said setting unit and said detecting means for sUpplying the high frequency current to said coil intermittently and for supplying the high frequency current to said coil for a predetermined period of time when it occurs.
 6. An induction hardening apparatus which comprises a turntable for supporting and rotating a workpiece to be induction hardened, and induction heating coil positioned in spaced apart relation to said turntable and to overlie the workpiece supported thereby, means for supplying a high frequency current to said coil to energize same and thereby induction heat portions of the workpiece passing by the coil during rotation of the workpiece by the turntable, means for delivering a quenching fluid to the workpiece to quench and thereby harden portions thereof that have been induction heated, and means responsive to the movement of said turntable and operable to regulate the energization of said coil by said high frequency current supply means in accordance with the angular position of the turntable to induction heat the workpiece intermittantly over angularly spaced regions.
 7. An induction hardening apparatus according to claim 6 wherein said heating coil is hollow to accommodate the flow of quenching fluid, and has apertures positioned to discharge quenching fluid against the workpiece. 